Abdominal aortic aneurysms (AAAs) and thoracic aortic aneurysms (TAAs) are diagnosed in approximately 250,000 and 20,000 patients respectively each year. Left untreated, these aneurysms commonly progress to rupture resulting in death. Prior to the advent of interventional catheter-based techniques, conventional surgical treatment has been the method of treatment for these lesions. Due to the often emergent condition of these patients and the potential for significant blood loss, high morbidity and mortality rates have been associated with this type of surgery.
With the introduction of catheter-based interventional techniques, new non-surgical therapies were made available to many patients. Since the initial animal work performed by Schatz et. al., small metallic tubes (i.e., stents) have been found to be of significant benefit for patients with coronary artery and peripheral artery disease. Schatz, R. A., Palmaz, J. C., Tio, F. O., Garcia, F., Garcia, O., Reuter, S. R. “Balloon-expandable intracoronary stents in the adult dog.” Circulation 76:450-7 (1987). In an effort to treat abdominal aortic aneurysms, Parodi et. al. reported on their experience with combining the barrier properties of synthetic vascular grafts with stent technology (i.e., stent-graft) to effectively inhibit blood flow into the aneurysm sac using catheter delivery systems. Parodi, J. C., Palmaz, J. C., Barone, H. D. “Transfemoral intraluminal graft implantation for abdominal aortic aneurysms.” Ann. Vasc. Surg 5:491-9 (1991).
This technology has continued to progress with significant improvements in successful device deployment and improved patient outcomes. Despite these improvements, there are many patients for which this technology is not applicable as a result of unique anatomical or disease conditions. Specifically, in the case of AAA disease, stent-graft devices typically require some amount of healthy vessel both proximal and distal to the aneurysm sac into which to place the stent-graft. In many patients, the proximal vessel is not long enough to achieve adequate fixation. Placement of the stent-graft in a more proximal location in these patients in order to achieve adequate fixation could partially or completely occlude the renal arteries providing blood to the kidneys. A number of different device designs have been proposed to allow device fixation to the aortic vessel proximal to the renal arteries (i.e., suprarenal fixation). Widespread applicability of supra-renal fixation devices has been limited by the flexibility of these designs, morphological variation of aneurysmal neck geometry across patients, and the coverage of the renal ostia with metallic stents which can act as a nidus for thromo-embolism of the renal circulation and/or hinder subsequent interventional access to this vasculature.
A similar situation exists for TAA disease. These aneurysmal lesions are often located in close proximity to the subclavian and carotid arterial branches. When inadequate proximal vascular tissue is available for anchoring the endoprosthesis, a suitable proximal anchoring zone can be created by performing a surgical transposition prior to the interventional procedure. This surgical approach is intended to assure continued flow to all vessels. Alternative means for achieving side-branch perfusion through the wall of a stent-graft are therefore desirable.
Other clinical conditions where there would be a benefit for fluid communication through the wall of a prosthesis are those involving cardiac surgery. Arterial blood leaving the heart serves to carry oxygen to the body. In contrast, venous blood is returned to the heart via the superior and inferior vena cava after releasing oxygen to the body and absorbing carbon dioxide and other waste products. Approximately 40,000 children are born each year with congenital heart defects. These abnormalities often involve a single functional ventricle and defects in the tissues (i.e., septum) separating the right (venous) and left (arterial) side of the heart. Mixing of arterial and venous blood in these patients results in reduced oxygen carrying capacity and often shortened life expectancies.
Cardiac surgical interventions performed for the most complex congenital heart abnormalities often require multiple surgical procedures to effect the final treatment for the patient. The Fontan procedure is an example of a staged surgical treatment that is designed to overcome these significant structural heart abnormalities and isolate systemic and pulmonary circulation at the definitive treatment. “Correction de l'atresie tricuspidienne.” Fontan, F., Mounicot, F. B., Baudet, E., Simonneau, J, Gordo, J., Gouffrant, J. M. Rapport de deux cas “corriges” par l'utilisation d'une technique chirurgicale nouvelle. [“Correction” of tricuspid atresia. 2 cases “corrected” using a new surgical technic] Ann-Chir-Thorac-Cardiovasc 10:39-47 (1971). Annecchino, F. P., Fontan, F., Chauve, A., Quaegebeur, J. “Palliative reconstruction of the right ventricular outflow tract in tricuspid atresia: a report of 5 patients.” Ann-Thorac-Surg. 29:317-21 (1980). Ottenkamp, J., Rohmer, J., Quaegebeur, J. M., Brom, A. G., Fontan, F. “Nine years' experience of physiological correction of tricuspid atresia: long-term results and current surgical approach.” Thorax 37:718-26 (1982). The surgical procedures must be staged to minimize the pressure and volume loads on the remaining functional single ventricle. In the first stage procedure, a connection is created between the Superior Vena Cava (SVC) and the Pulmonary Artery (PA). This is referred to as a Hemi-Fontan or Glenn Shunt procedure. Mathur, M., Glenn, W. W. “Rational approach to the surgical management of tricuspid atresia.” Circulation 37:1162-7 (1968). This shunt reduces the degree of venous and arterial blood mixing, and improves oxygenation of the blood.
Once the pulmonary circulation and functional ventricle are sufficiently developed, a subsequent procedure is performed wherein the blood going to the right ventricle is bypassed by routing the blood in the Inferior Vena Cava (IVC) directly to the PA by way of a baffle or tube connecting the IVC to the PA. At the time of this procedure, a small hole is typically created in the side of the connection tube to allow some flow of blood into the right ventricle. This small hole is considered a temporary connection that reduces the work for the remaining ventricle when pulmonary vascular resistance is elevated. Bridges, N. D., Mayer, J. E., Lock, J. E., Jonas, R. A., Hanley, F. L., Keane, J. F., Perry, S. B., Castaneda, A. R. “Effect of baffle fenestration on outcome of the modified Fontan operation.” Circulation 86:1762-9 (1992).
The final surgical procedure involves either surgical closure or transcatheter occlusion of the temporary hole in the IVC to PA connector tube. This multi-staged conventional surgical approach for patients with complex congenital heart disease is not optimal as it puts patients at additional risk of morbidity and mortality with each subsequent surgical intervention. This risk may be reduced if the first surgical intervention can set the stage for a future minimally invasive procedure that eliminates the need for additional open-heart surgery.
Various devices and design modifications have been proposed in an effort to provide access to anatomical structures surrounding the device or to internal spaces of the device.
U.S. Pat. No. 6,428,565, issued to Wisselink, and U.S. Pat. No. 6,395,018, issued to Castaneda, each relate to stent-graft systems with pre-formed apertures to allow for side-branch access. Neither of these devices have apertures that are closed at the time of initial implant.
U.S. Pat. No. 6,398,803, issued to Layne, et. al., relates to partially covered stents having various patterns of open apertures along the length of the device. As with the Wisselink and Castaneda devices, the apertures are fully formed prior to deployment of the device.
U.S. Pat. No. 6,432,127, issued to Kim, et. al., discloses formation of an aperture in the wall of a vascular conduit through the use of a cutting tool. The conduit does not provide a deformable framework encompassing the aperture formation site. As a result, targeting the precise location of the region in which to create the aperture is difficult to visualize using conventional imaging techniques. Moreover, the aperture is not reinforced along its peripheral regions once the aperture is formed. The absence of a framework delimiting the aperture formation site precludes precise sizing of the aperture during its formation.
There remains a need for a device that initially maintains the continuity and fluid-retaining properties of a wall portion of an implantable medical device, while providing means for forming a permanent aperture in the medical device. Such a device would permit custom sizing of the aperture in situ at the implant site during surgery.